O2 Oxygen Sensor Upstream Downstream for Nissan Altima (2004-2006) 2.5L

Direct-Fit Upstream & Downstream O2 Oxygen Sensor Kit for 2004-2006 Nissan Altima (L31)

What it Does: This matched upstream air-fuel ratio and downstream oxygen sensor kit restores closed-loop fueling precision and catalyst monitoring on the 2004-2006 Nissan Altima (L31) QR25DE 2.5L I4.

The Stock Nissan Altima O2 Sensor Failure

On the L31 Altima with the QR25DE 2.5L I4, factory oxygen sensors endure severe thermal cycling and exhaust carbon fouling. Over time, the zirconia sensing element degrades or suffers heater circuit burnout, slowing lambda response. Oil residue or coolant contamination also poisons the platinum electrodes, triggering stubborn P2A00, P0133, and P0031 codes while forcing the ECM into rich open-loop fueling.

Common Symptoms of a Failing OEM O2 Sensor

• Check Engine Light / DTCs: Persistent P2A00, P0133, or P0031 codes from slow sensor response or dead heaters.
• Rich Fuel Trims: Sluggish closed-loop feedback causes fouled spark plugs and reduced fuel economy.
• Drivability & Emissions Impact: Hesitation under throttle load and failed state emissions inspections.

The Direct-Fit Planar Zirconia Sensor Solution

Replacing both sensors together restores balanced exhaust feedback across the L31 exhaust stream. This matched kit pairs one upstream air-fuel ratio sensor with one downstream heated oxygen sensor featuring fast-light-off heaters and stainless housings. Factory-length harnesses and OEM-style weatherproof connectors plug directly into the QR25DE 2.5L I4 loom without splicing. Precision-cut threads ensure clean bolt-on seating in stock exhaust bungs.

What's Included

• 1 Upstream Air-Fuel Ratio Oxygen Sensor
• 1 Downstream Heated Oxygen Sensor

Technical Specifications

Compatibility

• 2004-2006 Nissan Altima 2.5L (QR25DE 2.5L I4 — Upstream & Downstream Positions)

Frequently Asked Questions & Fitment Warnings

Does this fit the L31 Altima?

Yes. Fits 2004-2006 Nissan Altima QR25DE 2.5L I4 models. Excludes 3.5L V6 Altima and Sentra 2.5L; confirm engine before ordering.

Will this clear P2A00, P0133, or P0031 codes?

Yes. Replacing failed sensors restores ECM lambda feedback and heater resistance to resolve P2A00, P0133, and P0031 after resetting codes.

Is wiring splicing required during installation?

No. Both sensors include OEM-style plug-and-play connectors for direct installation into factory exhaust bungs with no cutting or splicing.

The Nissan Precision Standard

Built for JDM durability, this matched set restores crisp throttle response and closed-loop efficiency, keeping your L31 QR25DE 2.5L I4 emissions-compliant and CEL-free.